Sealed switched reluctance motor

ABSTRACT

A motor including a sealed rotor with at least one salient rotor pole and a stator comprising at least one salient stator pole having an excitation winding associated therewith and interfacing with the at least one salient rotor pole to effect an axial flux circuit between the at least one salient stator pole and the at least one salient rotor pole.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. patent applicationSer. No. 14/540,055, filed on Nov. 13, 2014, now U.S. Pat. No.10,348,172, issued on Jul. 9, 2019, which is a non-provisional of andclaims the benefit of U.S. provisional patent application No. 61/903,792filed on Nov. 13, 2013, the disclosures of which are incorporated hereinby reference in their entireties.

BACKGROUND 1. Field

The exemplary embodiments generally relate to motors for use in vacuumor corrosive environments, for example, in substrate processingapparatus.

2. Brief Description of Related Developments

Generally, motors used in applications such as semiconductor fabricationare typically configured as brushless DC motors. A rotor for theseapplications may generally include a number of permanent magnetsincorporating rare earth materials. Special fixtures may be required tobond the permanent magnets to the rotor. Existing direct drivetechnology, which for example uses permanent magnet motors for actuationand optical encoders for position sensing, exhibits considerablelimitations when, for example, the magnets, bonded components, seals andcorrosive materials of the direct drive are exposed to ultra-high vacuumand/or aggressive and corrosive environments. In order to survivecorrosive or high vacuum environments, the permanent magnets aregenerally required to be encapsulated and sealed in order to avoidmagnet degradation.

Stators for these applications are usually constructed of laminatedferromagnetic material with complex slot shapes, multiple phases, andoverlapping coils. Construction of a conventional laminated statorrequires several complex manufacturing steps in order to assure properassembly, lamination bonding, coil winding and installation and propermachining to meet tight tolerances.

It would be advantageous to provide a rotor that is vacuum compatible,corrosion resistant, non-laminated, and that does not utilize rare earthmaterials. It would also be advantageous to use a non-laminated statorwith a simplified construction. It would further be advantageous toprovide a motor with a shorter flux path that results in lower eddycurrent and iron losses, and provides a higher torque capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the disclosed embodiment areexplained in the following description, taken in connection with theaccompanying drawings, wherein:

FIGS. 1A-1D show schematic views of substrate processing apparatus ortools in accordance with aspects of the disclosed embodiment;

FIG. 2 illustrates an exemplary motor in accordance with aspects of thedisclosed embodiment;

FIG. 3A illustrates an exemplary rotor in accordance with aspects of thedisclosed embodiment;

FIG. 3B illustrates an exemplary stator in accordance with aspects ofthe disclosed embodiment;

FIG. 4 shows a coil element in accordance with aspects of the disclosedembodiment;

FIG. 5 shows coil elements and associated stator poles in accordancewith aspects of the disclosed embodiment;

FIG. 6 shows an exemplary assembly a rotor, stator, and coil elements inaccordance with aspects of the disclosed embodiment;

FIGS. 7A-7C show different exemplary rotors in accordance with aspectsof the disclosed embodiment;

FIG. 8 shows a rotor, stator, and coil elements integrated into a robotdrive in accordance with aspects of the disclosed embodiment;

FIG. 9 shows an exemplary connection of coil elements in accordance withaspects of the disclosed embodiment;

FIG. 10 shows an exemplary axial flux motor in accordance with aspectsof the disclosed embodiment;

FIG. 11 shows A partial cross section of an axial flux motor inaccordance with aspects of the disclosed embodiment;

FIGS. 12A and 12B show flux flows in a conventional radial flux machineand an axial flux machine in accordance with aspects of the disclosedembodiment;

FIG. 13 illustrates an exemplary axial flux motor in accordance withaspects of the disclosed embodiment;

FIG. 14 shows a stator pole in accordance with aspects of the disclosedembodiment;

FIG. 15 illustrates a stator module, a rotor, and an isolation wall inaccordance with aspects of the disclosed embodiment;

FIG. 16 shows another aspect of an exemplary axial flux machine inaccordance with aspects of the disclosed embodiment;

FIG. 17A shows an exemplary rotor in accordance with aspects of thedisclosed embodiment;

FIG. 17B shows an exemplary rotor in accordance with aspects of thedisclosed embodiment;

FIG. 18A shows a top view of an exemplary set of stator windings and arotor in a step of an exemplary commutation sequence in accordance withaspects of the disclosed embodiment; and

FIGS. 18B-18H illustrate an exemplary commutation sequence in accordancewith aspects of the disclosed embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1A-1D, there are shown schematic views of substrateprocessing apparatus or tools incorporating the aspects of the disclosedembodiment as disclosed further herein.

Referring to FIGS. 1A and 1B, a processing apparatus, such as forexample a semiconductor tool station 1090 is shown in accordance with anaspect of the disclosed embodiment. Although a semiconductor tool isshown in the drawings, the aspects of the disclosed embodiment describedherein can be applied to any tool station or application employingrobotic manipulators. In this example the tool 1090 is shown as acluster tool, however the aspects of the disclosed embodiment may beapplied to any suitable tool station such as, for example, a linear toolstation such as that shown in FIGS. 1C and 1D and described in U.S.patent application Ser. No. 11/442,511, entitled “Linearly DistributedSemiconductor Workpiece Processing Tool,” filed May 26, 2006, thedisclosure of which is incorporated by reference herein in its entirety.The tool station 1090 generally includes an atmospheric front end 1000,a vacuum load lock 1010 and a vacuum back end 1020. In other aspects,the tool station may have any suitable configuration. The components ofeach of the front end 1000, load lock 1010 and back end 1020 may beconnected to a controller 1091 which may be part of any suitable controlarchitecture such as, for example, a clustered architecture control. Thecontrol system may be a closed loop controller having a mastercontroller, cluster controllers and autonomous remote controllers suchas those disclosed in U.S. Pat. No. 7,904,182, entitled “Scalable MotionControl System,” issued on Mar. 8, 2011, the disclosure of which isincorporated by reference herein in its entirety. In other aspects, anysuitable controller and/or control system may be utilized.

In one aspect, the front end 1000 generally includes load port modules1005 and a mini-environment 1060 such as for example an equipment frontend module (EFEM). The load port modules 1005 may be box opener/loaderto tool standard (BOLTS) interfaces that conform to SEMI standardsE15.1, E47.1, E62, E19.5 or E1.9 for 300 mm load ports, front opening orbottom opening boxes/pods and cassettes. In other aspects, the load portmodules may be configured as 200 mm wafer interfaces or any othersuitable substrate interfaces such as for example larger or smallerwafers or flat panels for flat panel displays. Although two load portmodules are shown in FIG. 1A, in other aspects any suitable number ofload port modules may be incorporated into the front end 1000. The loadport modules 1005 may be configured to receive substrate carriers orcassettes 1050 from an overhead transport system, automatic guidedvehicles, person guided vehicles, rail guided vehicles or from any othersuitable transport method. The load port modules 1005 may interface withthe mini-environment 1060 through load ports 1040. The load ports 1040may allow the passage of substrates between the substrate cassettes 1050and the mini-environment 1060. The mini-environment 1060 generallyincludes any suitable transfer robot 1013 which may incorporate one ormore aspects of the disclosed embodiment described herein. In one aspectthe robot 1013 may be a track mounted robot such as that described in,for example, U.S. Pat. No. 6,002,840, the disclosure of which isincorporated by reference herein in its entirety. The mini-environment1060 may provide a controlled, clean zone for substrate transfer betweenmultiple load port modules.

The vacuum load lock 1010 may be located between and connected to themini-environment 1060 and the back end 1020. It is noted that the termvacuum as used herein may denote a high vacuum such as 10−5 Torr orbelow in which the substrate are processed. The load lock 1010 generallyincludes atmospheric and vacuum slot valves. The slot valves may providethe environmental isolation employed to evacuate the load lock afterloading a substrate from the atmospheric front end and to maintain thevacuum in the transport chamber when venting the lock with an inert gassuch as nitrogen. The load lock 1010 may also include an aligner 1011for aligning a fiducial of the substrate to a desired position forprocessing. In other aspects, the vacuum load lock may be located in anysuitable location of the processing apparatus and have any suitableconfiguration.

The vacuum back end 1020 generally includes a transport chamber 1025,one or more processing station(s) 1030 and any suitable transfer robot1014 which may include one or more aspects of the disclosed embodimentsdescribed herein. The transfer robot 1014 will be described below andmay be located within the transport chamber 1025 to transport substratesbetween the load lock 1010 and the various processing stations 1030. Theprocessing stations 1030 may operate on the substrates through variousdeposition, etching, or other types of processes to form electricalcircuitry or other desired structure on the substrates. Typicalprocesses include but are not limited to thin film processes that use avacuum such as plasma etch or other etching processes, chemical vapordeposition (CVD), plasma vapor deposition (PVD), implantation such asion implantation, metrology, rapid thermal processing (RTP), dry stripatomic layer deposition (ALD), oxidation/diffusion, forming of nitrides,vacuum lithography, epitaxy (EPI), wire bonder and evaporation or otherthin film processes that use vacuum pressures. The processing stations1030 are connected to the transport chamber 1025 to allow substrates tobe passed from the transport chamber 1025 to the processing stations1030 and vice versa.

Referring now to FIG. 1C, a schematic plan view of a linear substrateprocessing system 2010 is shown where the tool interface section 2012 ismounted to a transport chamber module 3018 so that the interface section2012 is facing generally towards (e.g. inwards) but is offset from thelongitudinal axis X of the transport chamber 3018. The transport chambermodule 3018 may be extended in any suitable direction by attaching othertransport chamber modules 3018A, 3018I, 3018J to interfaces 2050, 2060,2070 as described in U.S. patent application Ser. No. 11/442,511,previously incorporated herein by reference. Each transport chambermodule 3018, 3019A, 3018I, 3018J includes any suitable substratetransport 2080, which may include one or more aspects of the disclosedembodiment described herein, for transporting substrates throughout theprocessing system 2010 and into and out of, for example, processingmodules PM. As may be realized, each chamber module may be capable ofholding an isolated or controlled atmosphere (e.g. N2, clean air,vacuum).

Referring to FIG. 1D, there is shown a schematic elevation view of anexemplary processing tool 410 such as may be taken along longitudinalaxis X of the linear transport chamber 416. In the aspect of thedisclosed embodiment shown in FIG. 1D, tool interface section 12 may berepresentatively connected to the transport chamber 416. In this aspect,interface section 12 may define one end of the tool transport chamber416. As seen in FIG. 1D, the transport chamber 416 may have anotherworkpiece entry/exit station 412 for example at an opposite end frominterface station 12. In other aspects, other entry/exit stations forinserting/removing workpieces from the transport chamber may beprovided. In one aspect, interface section 12 and entry/exit station 412may allow loading and unloading of workpieces from the tool. In otheraspects, workpieces may be loaded into the tool from one end and removedfrom the other end. In one aspect, the transport chamber 416 may haveone or more transfer chamber module(s) 18B, 18 i. Each chamber modulemay be capable of holding an isolated or controlled atmosphere (e.g. N2,clean air, vacuum). As noted before, the configuration/arrangement ofthe transport chamber modules 18B, 18 i, load lock modules 56A, 56B andworkpiece stations forming the transport chamber 416 shown in FIG. 1D ismerely exemplary, and in other aspects the transport chamber may havemore or fewer modules disposed in any desired modular arrangement. Inthe aspect shown, station 412 may be a load lock. In other aspects, aload lock module may be located between the end entry/exit station(similar to station 412) or the adjoining transport chamber module(similar to module 18 i) may be configured to operate as a load lock. Asalso noted before, transport chamber modules 18B, 18 i have one or morecorresponding transport apparatus 26B, 26 i, which may include one ormore aspects of the disclosed embodiment described herein, locatedtherein. The transport apparatus 26B, 26 i of the respective transportchamber modules 18B, 18 i may cooperate to provide the linearlydistributed workpiece transport system 420 in the transport chamber. Inthis aspect, the transport apparatus 26B may have a general SCARA armconfiguration (though in other aspects the transport arms may have anyother desired arrangement such as a frog-leg configuration, telescopicconfiguration, bi-symmetric configuration, etc.). In the aspect of thedisclosed embodiment shown in FIG. 1D, the arms of the transportapparatus 26B may be arranged to provide what may be referred to as fastswap arrangement allowing the transport to quickly swap wafers from apick/place location as will also be described in further detail below.The transport arm 26B may have a suitable drive section, such as thatdescribed below, for providing each arm with any suitable number ofdegrees of freedom (e.g. independent rotation about shoulder and elbowjoints with Z axis motion). As seen in FIG. 1D, in this aspect themodules 56A, 56, 30 i may be located interstitially between transferchamber modules 18B, 18 i and may define suitable processing modules,load lock(s), buffer station(s), metrology station(s) or any otherdesired station(s). For example the interstitial modules, such as loadlocks 56A, 56 and workpiece station 30 i, may each have stationaryworkpiece supports/shelves 56S, 56S1, 56S2, 30S1, 30S2 that maycooperate with the transport arms to effect transport or workpiecesthrough the length of the transport chamber along linear axis X of thetransport chamber. By way of example, workpiece(s) may be loaded intothe transport chamber 416 by interface section 12. The workpiece(s) maybe positioned on the support(s) of load lock module 56A with thetransport arm 15 of the interface section. The workpiece(s), in loadlock module 56A, may be moved between load lock module 56A and load lockmodule 56 by the transport arm 26B in module 18B, and in a similar andconsecutive manner between load lock 56 and workpiece station 30 i witharm 26 i (in module 18 i) and between station 30 i and station 412 witharm 26 i in module 18 i. This process may be reversed in whole or inpart to move the workpiece(s) in the opposite direction. Thus, in oneaspect, workpieces may be moved in any direction along axis X and to anyposition along the transport chamber and may be loaded to and unloadedfrom any desired module (processing or otherwise) communicating with thetransport chamber. In other aspects, interstitial transport chambermodules with static workpiece supports or shelves may not be providedbetween transport chamber modules 18B, 18 i. In such aspects, transportarms of adjoining transport chamber modules may pass off workpiecesdirectly from end effector or one transport arm to end effector ofanother transport arm to move the workpiece through the transportchamber. The processing station modules may operate on the substratesthrough various deposition, etching, or other types of processes to formelectrical circuitry or other desired structure on the substrates. Theprocessing station modules are connected to the transport chambermodules to allow substrates to be passed from the transport chamber tothe processing stations and vice versa. A suitable example of aprocessing tool with similar general features to the processingapparatus depicted in FIG. 1D is described in U.S. patent applicationSer. No. 11/442,511, previously incorporated by reference in itsentirety.

FIG. 2 shows an exemplary motor 2000 integrated into a robot drive 2005.Robot drive 2005 may be suitable for use with any direct drive orrobotic drive application, for example, transfer robot 1013, transferrobot 1014, substrate transport 2080, or transport arm 26B. Motor 2000may include, at least one stator pole 2010, a coil element 2015, and arotor 2020. In the aspects shown in FIG. 2, the stator pole 2010 andassociated coil element 2015 are positioned in a separate environment2025, sealed from rotor 2020. The rotor 2020 may be located in a highvacuum high vacuum (e.g. approximately 10−5 Torr or lower) or corrosiveenvironment, and may be separated from the stator pole 2010 and coilelement 2015 by a non-magnetic isolation wall 2030. The stator pole 2010and coil element 2015 may be located in an atmospheric pressureenvironment. The exemplary embodiment depicted in the figures has whatmay be referred to as a rotary drive configuration that is illustratedfor purposes of facilitating description and features of the variousaspects, as shown and described herein. As may be realized the featuresof the various aspects illustrated with respect to the rotary driveconfiguration are equally applicable to a linear drive configuration.

The aspects of the disclosed embodiment described herein may be employedfor vacuum or atmospheric robot applications where the rotor and othermoving parts are isolated from stationary motor components, for examplestator poles and associated coil elements. Generally the aspects of thedisclosed embodiment include one or more switched reluctance rotors foroperating any suitable direct drive or robot drive. The moving parts ofthe direct or robot drive may be located within a sealed or otherwiseisolated environment which can include a controlled environment such asa vacuum environment, suitable for semiconductor processing such as maybe expected in a transport chamber of a semiconductor processing tool asdescribed further herein. The moving parts of the direct or robot drivemay be located within an atmospheric pressure environment. Anon-magnetic separation or isolation wall made of any suitable materialmay be disposed between the moving parts of the drive, for example therotor, and the stationary parts of the drive, for example, the statorpole and coil element.

FIG. 3 illustrates a rotor 100 in accordance with an aspect of thedisclosed embodiment. Although the aspects of the disclosed embodimentwill be described with reference to the drawings, it should beunderstood that the aspects of the disclosed embodiment can be embodiedin many forms. In addition, any suitable size, shape or type of elementsor materials could be used.

The aspects of the disclosed embodiment described herein may be employedfor vacuum or atmospheric motor applications where the rotor may belocated within a sealed, isolated environment separated from the statorby an isolation wall. The sealed environment may be a vacuum oratmospheric environment and the isolation wall may be made ofnon-magnetic material.

FIG. 3A shows an exemplary rotor 100 with at least one salient rotorpole 105 arranged around the perimeter of the rotor. FIG. 3B illustratesan exemplary stator 200 with at least one salient stator pole 205. Whilethe rotor 100 is shown as having 6 salient poles and the stator 200 isshown as having 8 salient poles it should be understood that the rotor100 and stator 200 may include any suitable number of salient poles.

The rotor 100 may be made by machining, extrusion, sintering, casting,or any suitable process, provided proper treatment is used to avoidoutgassing, such as when subjected to a high vacuum environment. Ifrequired, the rotor 100 may be superficially treated, such as by coatingwith a material suitable to render rotor usable in a high vacuum. Therotor 100 may generally have a non-laminated construction, and may beconstructed of a solid piece of ferromagnetic material, for example,soft magnetic iron or steel, such as 400 series stainless steel. In atleast one exemplary aspect, the rotor may be made of a compositematerial, for example a material that combines high magneticpermeability and flux density with low electrical conductivity. Suchmaterial may be effective in reducing the effect of core losses due toeddy currents resulting from the rate of change of the magnetic fluxbetween the rotor and stator poles. It should be noted that a suitabletreatment may be required to prevent outgassing by the rotor, inparticular when used in a high vacuum environment.

Table 1 below shows a table of exemplary composite materials and theirrelative permeability and saturation flux density, as compared withnon-composite materials, for example, carbon and stainless steel.

TABLE 1 RELATIVE SATURATION MATERIAL PERMEABILITY FLUX DENSITY (T)Vacoflux 50 4500 2.1 Vacoflux 17 3500 1.5 Chrome Core 13-XP Alloy 32001.7 Chrome Core 8 Alloy 3100 1.86 Chrome Core 8-FM Alloy 3100 1.86Chrome Core 12-FM Alloy 3100 1.77 Chrome Core 13-FM Alloy 2900 1.7 430FR Solenoid Quality 2600 1.5 Stainless 430 F Solenoid Quality 2000 1.6Stainless 1018 Carbon Steel 795 2.4 416 Stainless 750 1.5

In at least another exemplary aspect, the rotor 100 may be constructedof a non-ferromagnetic core with at least one salient rotor poleconstructed of a ferromagnetic material.

The stator 200 may also have a non-laminated construction and may bemade by machining, extrusion, sintering, casting, or any suitableprocess. In at least one exemplary aspect, the stator 200 may also bemade of a composite material, for example, as stated above, a materialthat combines high magnetic permeability and flux density with lowelectrical conductivity, examples of which are shown in Table 3.

FIG. 4 shows a coil element 400 suitable for use with the stator 200.The coil element 400 is constructed as an individually wound elementthat provides a phase winding that is independent of other phasewindings. Coil element 400 is provided with a form factor that allowsthe coil element 400 to be integrated with an individual stator pole205.

In the aspects shown in FIG. 5, the coil element 400 is configured to bemounted on, or to surround an associated stator pole 205 and to providean excitation field for the associated stator pole 205.

FIG. 6 shows an exemplary assembly 600 of the rotor 100, stator 200, andcoil elements 400. In the exemplary assembly 600 the rotor 100 ispositioned within the stator 200 with the rotor poles 105 facing thestator poles 205.

FIGS. 7A-7C show different exemplary rotors suitable for use with thedisclosed embodiment. FIG. 7A shows a solid rotor 700 with poles 705having a larger axial dimension that the rotor body 710. As may berealized, the arrangement illustrated in FIGS. 7A-7C is exemplary, andin alternate aspects of the disclosed embodiment FIG. 7B shows a rotor715 with a similar configuration but with a non-ferromagnetic core 720and at least one salient rotor pole 725 constructed of a ferromagneticmaterial. In another aspect, FIG. 7C shows a rotor 730 with laminated orwhat may be referred to as generally comb shaped poles 735 forminimizing eddy currents when subjected to a varying magnetic field ofinteracting stator poles. Grooves 740 or laminations may have anysuitable orientation to minimize eddy currents. In one aspect statorpoles 205 may also be comb shaped.

FIG. 8 shows the rotor 100, stator 200, and coil elements 400 integratedinto a robot drive. In the aspects shown in FIG. 8, the stator 200 andcoil elements 400 associated with each stator pole 205 are positioned ina separate environment 810 from the rotor 100. The rotor 100 may locatedin an ultra-high vacuum or corrosive environment, separated from thestator 200 and coil elements 400 by a non-magnetic isolation wall 820.The stator 200 and coil elements 400 may be located in an atmosphericpressure environment.

FIG. 9 shows an example of how the coil elements 400 may be connected toeffect a flux field for driving the rotor 100. In the aspects shown inFIG. 9, the coil elements are configured as 4 independent pairs of coilswhere members of each pair are diametrically opposed to each other. Eachpair is defined as a motor phase, thus the aspects shown in FIGS. 5, 6and 8 are configured as a 4-phase machine. It should be understood thatrotor 100 and stator 200 may be configured with any number of poles, andany suitable number of coil elements 400 may be used to implement anynumber of phases.

FIG. 10 shows an exemplary axial flux motor 1000 utilizing rotor 100. Astator 1005 of the axial flux motor 1000 is an assembly of independentmodules 1010 arranged around the rotor 100 that each include a statorpole 1015 and an independent phase winding 1020.

For exemplary purposes only, the axial flux motor in FIG. 10 isconfigured with a 6 pole rotor and an 8 pole stator, but in otheraspects any suitable number of rotor and stator poles may be employed.In at least one aspect, diametrically opposed stator modules are wiredto the same phase. The phase windings of the modules comprising a phasemay be wound in series or parallel.

A partial cross section of the axial flux motor is shown in FIG. 11.Stator module 1010 may have a stator pole 1015 which may include endmembers 1025, 1030 which extend radially toward the rotor from aconnecting member 1035, and may overlap at least a portion of rotor pole105. The stator pole 1015 may be constructed of soft-magnetic steel orother suitable material as discussed above. As shown by arrow 1100 theflux path is axial from the stator pole 915 through the rotor pole 105.

FIGS. 12A and 12B show the differences in the flow of flux lines in aconventional radial flux machine and an axial flux machine,respectively. In the radial flux machine, flux flows radially acrossdiametrically opposite poles 1201, 1202 of the rotor andcircumferentially through the stator, while in the axial flux machine,the flux flows axially and the flux lines are confined to the statormodule 1010 and interfacing rotor pole 1205.

According to at least one aspect, the total flux flow in each phase ofthe axial flux motor may be divided to flow through two parallel paths,in contrast with a radial flux machine where the flux flow through thewindings is in series. A parallel flux flow may provide lower fluxdensity levels and allows for operation below flux density saturationlevels. When operating at unsaturated flux density levels, torquecapacity generally increases as a quadratic function of current while inat saturated levels, torque capacity generally increases as a linearfunction of current. Thus, lower flux levels in the axial machine resultin higher torque capacity, for the same current levels. Furthermore,because the effective air gap in an axial flux motor extends in an axialdirection, rotor wobble produces no net change in the air gap andresults in no torque ripple.

An exemplary axial flux motor with a 3-pole rotor 1305 and a 4-polestator 1310 is shown in FIG. 13. In this aspect, each stator phase isconfined to a single stator module 1315 providing lower manufacturingand assembly costs and simpler wiring arrangements.

FIG. 14 shows another aspect of a stator pole 1405 in accordance withthe disclosed embodiment. While the stator pole 1015 is shown arectangular cross section in FIG. 10, the stator pole 1405 may have aportion with a circular cross section 1410 to enable ease of windingphase coils around the stator pole. A stator pole with a rectangularcross-section may have windings with a fill factor of approximately 0.6,while a stator pole with a circular cross-section may have windings thatmay exceed a fill factor of approximately 0.8. A higher fill factor mays result in higher motor torque capacity. FIG. 15 illustrates usage ofat least one stator module 1510 and a rotor 1515 in combination with anisolation wall 1520 similar to aspects described above. In one aspect,the isolation wall 1520 provides a seal for separating the environmentsof the stator module 1510 and the rotor 1515. For example, the rotor1515 may be located in an ultra-high vacuum or corrosive environment,while the stator module may be located in an atmospheric environment. Inone aspect, the isolation wall provides a seal that conforms to anoutline between the extending members 1530, 1535 of the stator pole 1525and the rotor 1515. In another aspect, the isolation wall provides aseal portion 1520′ between the separate environments that surrounds oneor more of the extending members 1530, 1535 of the stator pole 1525, orsurrounds the stator pole itself. In other aspects, the isolation wallmay be integrated with the stator pole. Suitable seals may includestatic seals such as sealing gaskets or rings suitable for ultra-highvacuum use. Further aspects of suitable seals are shown and described inU.S. Application No. 61/903,813, filed Nov. 13, 2013 entitled “SealedRobot Drive,” filed coincidently and incorporated by reference herein inits entirety.

FIG. 16 shows another aspect of an exemplary axial flux machine 1600.Axial flux machine 1600 includes a stator 1605 constructed of anassembly of independent stator modules 1610 arranged around a rotor1615. Each stator module 1610 includes a stator pole 1620 and anindependent phase winding 1625. Rotor 1615 includes at least one salientrotor pole 1630. In one aspect, the salient rotor pole 1630 may includeend members 1635, 1640 extending toward the stator assembly 1605. In atleast one aspect, the arrangement of stator and rotor poles facilitatesinstallation and removal of the rotor without interfering with thestator assembly 1605. According to one or more aspects, the statormodules 1610 are independent, for example, may individually be added orremoved from any suitable location on the stator. Each stator module1610 may include a stator pole and an excitation coil installed togetheras a unit. The stator 1605 may include a selectable number of statormodules 1610 arranged around the stator that may be interchangeableamong each other. In at least one aspect, the stator 1605 may beconfigurable by selecting the number of stator modules 1610 to beinstalled on the stator.

FIG. 17A shows an exemplary rotor 1700 according to another aspect ofthe disclosed embodiment. Rotor 1700 may be configured as a switchedreluctance motor, may generally have a non-laminated solid construction,and may be constructed of ferromagnetic material, for example, softmagnetic iron or steel. In one aspect, the rotor may be made of acomposite material, for example a material that combines high magneticpermeability and flux density with low electrical conductivity. In oneaspect, the rotor 1700 may be constructed of a non-ferromagnetic corewith at least one salient rotor pole constructed of a ferromagneticmaterial.

The at least one salient rotor pole 1710 may comprise a set of axiallydisplaced sub-poles X, Y. Sub-poles X, Y may be offset by an electricalangle. The arrangement of the sub-poles X, Y allows use of the switchedreluctance rotor 1700 with a stator configured as a DC brushless stator.

FIG. 17B shows another exemplary rotor 1715, where sub-poles X,Y aremounted on a backing 1720. Backing 1720 may also include end membersextending radially to effect an axial flux flow as discussed for theaxial flux machine 1610 above.

Precise position control may be achieved by providing bi-directionalforces to the rotor, for example, by using at least 2 sets ofindependently energized windings, where each one generates attractiveforces in an opposing direction. FIG. 18A shows a top view of anexemplary set of stator windings 1805 and the rotor 1700 in a first stepof an exemplary commutation sequence that provides the attractive forcesin opposing directions. FIGS. 18B-18H illustrate the remaining steps 2-8of the exemplary sequence.

Table 2 below shows the exemplary commutation sequence, an approximateactuation force, and the sub-poles subjected to force, for each step ofthe exemplary sequence.

TABLE 2 Rotor Step A B C D E F Actuation Force poles feeling force 1 0 11 0 1 1 −k_(B)i_(B) ² + k_(E)i_(E) ² − k_(C)i_(C) ² + k_(F)i_(F) ² Y 2 10 1 1 0 1 −k_(A)i_(A) ² + k_(D)i_(D) ² − k_(F)i_(F) ² + k_(C)i_(C) ² X/Y3 1 1 0 1 1 0 −k_(A)i_(A) ² + k_(D)i_(D) ² − k_(B)i_(B) ² + k_(E)i_(E) ²X 4 0 1 1 0 1 1 −k_(B)i_(B) ² + k_(E)i_(E) ² − k_(C)i_(C) ² + k_(F)i_(F)² X 5 1 0 1 1 0 1 −k_(C)i_(C) ² + k_(F)i_(F) ² − k_(D)i_(D) ² +k_(A)i_(A) ² X/Y 6 1 1 0 1 1 0 −k_(D)i_(D) ² + k_(A)i_(A) ² − k_(E)i_(E)² + k_(B)i_(B) ² Y 7 0 1 1 0 1 1 −k_(E)i_(E) ² + k_(B)i_(B) ² −k_(F)i_(F) ² + k_(C)i_(C) ² Y 8 1 1 0 1 1 0 −k_(D)i_(D) ² + k_(A)i_(A) ²− k_(F)i_(F) ² + k_(B)i_(B) ² X/Y

The stator may include two independent sets of three phase windings ABCand DEF. Each three phase winding set ABC, DEF may be wound similar tothat of a conventional 3-phase brushless motor. In FIG. 18A, the two3-phase winding sets ABC, DEF alternate around the stator. Theconfiguration of the rotor sub-poles are such that at any rotorposition, a resultant electromagnetic propulsion force on the rotor isbi-directional. The bi-directional forces provide for position controlas mentioned above. Position control may be implemented by commutatingthe stator currents such that at any rotor position, 2 out of the 6winding phases exert a force on the rotor in one direction and 2 otherwinding phases exert a force on the rotor in the opposite direction. Theaxial flux flow discussed above provides for minimizing the reluctancein the magnetic flux circuit in order to maximize the field strengthflowing through the windings.

It should be noted that when stator windings A and D are connected inseries, B and E are connected in series, and C and F are connected inseries, the stator of a 6-phase variable reluctance motor behavesidentical to the stator of a 3-phase DC brushless motor. Thus, the samestator can be used in two different types of motors, switched reluctanceand DC brushless motors.

In accordance with one or more aspects of the disclosed embodiment amotor includes a sealed rotor with at least one salient rotor pole astator comprising at least one salient stator pole having an excitationwinding associated therewith and interfacing with the at least onesalient rotor pole to effect an axial flux circuit between the at leastone salient stator pole and the at least one salient rotor pole.

In accordance with one or more aspects of the disclosed embodiment, eachsalient rotor pole comprises a set of axially displaced sub-poles.

In accordance with one or more aspects of the disclosed embodiment, theat least one salient rotor pole is sealed from the at least one salientstator pole.

In accordance with one or more aspects of the disclosed embodiment, theat least one salient stator pole has sub poles.

In accordance with one or more aspects of the disclosed embodiment, eachsalient rotor pole comprises a set of sub-poles offset by an electricalangle.

In accordance with one or more aspects of the disclosed embodiment, thesealed rotor comprises a non-magnetic core and the at least one salientrotor pole is ferromagnetic.

In accordance with one or more aspects of the disclosed embodiment, theat least one salient rotor pole is mounted on a ferromagnetic backing.

In accordance with one or more aspects of the disclosed embodiment, theferromagnetic backing comprises members extending radially toward the atleast one salient stator pole to effect the axial flux flow circuit.

In accordance with one or more aspects of the disclosed embodiment, theat least one salient stator pole is configured as a slot through whichthe at least one salient rotor pole passes to effect the axial flux flowcircuit.

In accordance with one or more aspects of the disclosed embodiment, theat least one salient rotor pole and at least one salient stator pole areconfigured with facing end members to effect the axial flux flowcircuit.

In accordance with one or more aspects of the disclosed embodiment, amotor includes a rotor having two sets of rotor poles offset by anelectrical angle, configured for at least three phase excitation.

In accordance with one or more aspects of the disclosed embodiment, amotor includes a rotor configured as a switched reluctance rotor; and astator configured as a brushless stator separated from the rotor by asealed partition.

In accordance with one or more aspects of the disclosed embodiment, therotor and stator are configured to generate an axial flux flow in themotor.

In accordance with one or more aspects of the disclosed embodiment, therotor comprises at least one salient rotor pole.

In accordance with one or more aspects of the disclosed embodiment, theat least one salient rotor pole is mounted on a ferromagnetic backingcomprising members extending toward the stator to effect the axial fluxflow.

In accordance with one or more aspects of the disclosed embodiment, therotor comprises at least one salient rotor pole comprising a set ofaxially displaced sub-poles.

In accordance with one or more aspects of the disclosed embodiment, thestator comprises independent sets of at least three phase windings.

In accordance with one or more aspects of the disclosed embodiment, thestator comprises a set of independent stator modules, each comprising astator pole and an excitation coil.

In accordance with one or more aspects of the disclosed embodiment, themotor includes an arrangement of rotor poles and stator poles configuredto apply attractive forces to the rotor.

In accordance with one or more aspects of the disclosed embodiment, amotor includes a rotor comprising a plurality of poles; a statorcomprising a plurality of independent stator modules arranged around therotor, the stator modules comprising salient stator poles constructed asseparate segments.

In accordance with one or more aspects of the disclosed embodiment, therotor poles and stator poles are arranged to effect a flux flow axial tothe rotor.

In accordance with one or more aspects of the disclosed embodiment, therotor comprises a non-magnetic core and ferromagnetic rotor poles.

In accordance with one or more aspects of the disclosed embodiment, therotor comprises members extending radially toward the stator to effectthe axial flux flow.

In accordance with one or more aspects of the disclosed embodiment, thestator segments are configured as slots through which the rotor polespass to effect the flux flow axial to the rotor.

In accordance with one or more aspects of the disclosed embodiment, therotor poles and stator segments are configured with facing end membersto effect the flux flow axial to the rotor.

In accordance with one or more aspects of the disclosed embodiment, amotor includes a rotor comprising a plurality of salient poles; and astator comprising at least one interchangeable stator module comprisinga stator pole and an excitation coil installed together as a unit.

In accordance with one or more aspects of the disclosed embodiment, amotor includes a rotor comprising a plurality of salient poles; and astator comprising a selectable number of interchangeable stator moduleseach defining an individual stator pole.

In accordance with one or more aspects of the disclosed embodiment, amotor includes a rotor comprising a plurality of salient poles; and aconfigurable stator, comprising at least one interchangeable statormodule comprising a stator pole and an excitation coil installedtogether as a unit, wherein the stator configuration is effected byselection of a number of stator modules installed on the stator.

It should be understood that the foregoing description is onlyillustrative of the aspects of the disclosed embodiment. Variousalternatives and modifications can be devised by those skilled in theart without departing from the aspects of the disclosed embodiment.Accordingly, the aspects of the disclosed embodiment are intended toembrace all such alternatives, modifications and variances that fallwithin the scope of the appended claims. Further, the mere fact thatdifferent features are recited in mutually different dependent orindependent claims does not indicate that a combination of thesefeatures cannot be advantageously used, such a combination remainingwithin the scope of the aspects of the invention.

What is claimed is:
 1. A motor comprising: a rotor configured as aswitched reluctance rotor, and having two sets of rotor poles offset byan electrical angle, configured for at least three phase excitation; anda stator configured as a brushless stator separated from the rotor by asealed partition.
 2. The motor of claim 1, wherein the rotor and statorare configured to generate an axial flux flow in the motor.
 3. The motorof claim 2, wherein the rotor comprises at least one salient rotor pole.4. The motor of claim 3, wherein the at least one salient rotor pole ismounted on a ferromagnetic backing comprising members extending towardthe stator to effect the axial flux flow.
 5. The motor of claim 4,wherein the ferromagnetic backing comprises members extending radiallytoward at least one salient stator pole of the stator to effect theaxial flux flow circuit.
 6. The motor of claim 1, wherein the rotorcomprises at least one salient rotor pole comprising a set of axiallydisplaced sub-poles.
 7. The motor of claim 1, wherein the statorcomprises independent sets of at least three phase windings.
 8. Themotor of claim 1, wherein the stator comprises a set of independentstator modules, each comprising a stator pole and an excitation coil. 9.The motor of claim 1, further comprising an arrangement of rotor polesand stator poles configured to apply attractive forces to the rotor. 10.The motor of claim 1, wherein the rotor comprises a non-magnetic coreand includes at least one salient rotor pole being ferromagnetic. 11.The motor of claim 1, wherein the stator includes at least one salientstator pole configured as a slot through which at least one salientrotor pole of the rotor passes to effect the axial flux flow circuit.12. The motor of claim 11, wherein the at least one salient rotor poleand at least one salient stator pole are configured with facing endmembers to effect the axial flux flow circuit.
 13. A motor comprising: arotor comprising a plurality of poles; and a stator comprising aplurality of independent stator modules arranged around the rotor, thestator modules comprising salient stator poles constructed as separatesegments.
 14. The motor of claim 13, wherein the rotor comprises anon-magnetic core and ferromagnetic rotor poles.
 15. The motor of claim13, wherein the rotor poles and stator poles are arranged to effect aflux flow axial to the rotor.
 16. The motor of claim 15, wherein therotor comprises members extending radially toward the stator to effectthe axial flux flow.
 17. The motor of claim 15, wherein the statorsegments are configured as slots through which the rotor poles pass toeffect the flux flow axial to the rotor.
 18. The motor of claim 15,wherein the rotor poles and stator segments are configured with facingend members to effect the flux flow axial to the rotor.
 19. The motor ofclaim 13, wherein at least one of the stator modules comprising salientstator poles is disposed so as to interface sub-poles of at least one ofa salient rotor pole of the plurality of poles.
 20. A motor comprising:a rotor comprising a plurality of salient poles; and a configurablestator comprising at least one interchangeable stator module comprisinga stator pole and an excitation coil installed together as a unit,wherein the stator configuration is effected by selection of a number ofstator modules installed on the stator.
 21. The motor of claim 20,wherein the rotor comprises a non-magnetic core and ferromagnetic rotorpoles.
 22. The motor of claim 20, wherein the rotor poles and statorpoles are arranged to effect a flux flow axial to the rotor.
 23. Themotor of claim 22, wherein the rotor comprises members extendingradially toward the stator to effect the axial flux flow.
 24. The motorof claim 22, wherein the stator modules are configured as slots throughwhich the rotor poles pass to effect the flux flow axial to the rotor.25. The motor of claim 22, wherein the rotor poles and stator modulesare configured with facing end members to effect the flux flow axial tothe rotor.
 26. The motor of claim 20, wherein at least one of the statormodules comprising salient stator poles is disposed so as to interfacesub-poles of at least one of a salient rotor pole of the plurality ofpoles.
 27. A motor comprising: a rotor comprising a plurality of salientpoles; and a stator comprising a selectable number of interchangeablestator modules each defining an individual stator pole.
 28. The motor ofclaim 27, wherein the rotor comprises a non-magnetic core andferromagnetic rotor poles.
 29. The motor of claim 27, wherein the rotorpoles and stator poles are arranged to effect a flux flow axial to therotor.
 30. The motor of claim 29, wherein the rotor comprises membersextending radially toward the stator to effect the axial flux flow. 31.The motor of claim 29, wherein the stator modules are configured asslots through which the rotor poles pass to effect the flux flow axialto the rotor.
 32. The motor of claim 29, wherein the rotor poles andstator modules are configured with facing end members to effect the fluxflow axial to the rotor.
 33. The motor of claim 27, wherein at least oneof the stator modules comprising salient stator poles is disposed so asto interface sub-poles of at least one of a salient rotor pole of theplurality of poles.